Help finding potentiometer replacement

[Beavs]

I have never try to extend the shaft of the potentiometers. What I would do is to use a lathe to make a part from aluminium. Alternatively, if you find a bushing (could be a plastic bushing or tube you may be able to glue a piece of potentiometer shaft.
But Alpha makes many types pf potentiometers and they also make some with a round shaft. You need to search in TAYDA. Mouser also carries this brand but I do not know if they will have the MN type. There are some on ebay.
What happened to the original part is it damaged?.

The original pot was dirty/corroded when I got it. I've cleaned/flushed it multiple times and it still isn't operating as would be expected but has gotten much better. The right channel will fully drop out when balancing to the right at about 2:30 or so, also seems to be finnicky at the center detent position.

I had wondered about the curves that I was seeing on other potentiometers and wondered how/when you would know that the two gangs were inverse of each other because everything I was seeing was just a single taper. That plot for the MN is what I was thinking I should see on the taper plots but never could find one...key being the MN vs linear/audio/15A etc. I think I can make the serrated and shorter shaft work on the Alpha pot you linked. Found this little coupler and then finding 6mm shaft to cut down is no problem. https://www.robotshop.com/en/jsumo-set-screw-shaft-coupler-6mm-6mm-pair.html

I've looked for other 100K pots with the MN taper and it seems that Alpha is about the only MN taper rotary potentiometers out there which seems very odd. Alps only shows 15A and 1B from what I can find. Surely there's other MN taper rotary potentiometers out there right? I'm fine with using the Alpha, coupler, and cut down smooth shaft for the time being though and thank you very much Jose for the help.

 

[JoseHH]

Alps and Noble custom-made these potentiometers specificaly for the audio companies in Japan. A related issue is the volume potentometers with loudness tap, which are not normally made and stocked by Alps. Outside of their base catalog, they only produce large orders on special request. There several taper curves, like inverse audio, W taper (also used for balance but is a cheaper, single gang control). Alpha makes acceptable products, but not as good as Alps or Noble or Bourns, but give it a try and see if it solves the problem. Bourns also makes MN potentiometers. Mouser may have some Bourns potentiometers but I do not know if they have this one. You can write an email to Mouser, because they have some products that do not show up in their search.
The coupler you found is nice but even a plastic tube that fits snuggly will work. All the serrateions and the split shaft could in princiiple be filed up with slight excess of epoxy resin and sanded down to a smooth cylinder after curing the resin.

 

[Beavs]

@Beavs, thanks for writing this for me. And sorry for hijacking your post.

I kind of understand it now, still new to this hobby. The grease I saw is to lubricate the turning shaft and nothing to do with the actual conductive and resistance electricity function (wiper maybe it is called?). So the D5 and F5 are the ones to clean and lubricate them to restore to their original state.

I saw this post about how member leesonic replaced his pot and hope will help a bit. Will also interest in what you find and resources so I can find mine

https://audiokarma.org/forums/index.php?threads/technics-su-v85a-amplifier-restoration.963896/

I stand corrected on the grease being detrimental if it migrated to the body of the pot. I ordered parts to replace the pot per the info from @JoseHH above, but those will probably be a while before arriving so I felt the need to keep tinkering with the original pot. I improved the response of the original pot with more cleanings/flushings using D5 and F5. The thin oil or lube in the F5 would dry out after a few days and the pot would get very gritty when turning it. I started searching more on lubrication for the pots and I was wrong about the grease being a large issue as it seems that was the original lubrication used for the wiper on the carbon trace. @Retrovert posts in this thread pushed me to use the Super Lube grease and it entirely smoothed out the grittiness with no ill effects on operation of the potentiometer:
https://audiokarma.org/forums/index...deoxit-f100-for-carbon-potentiometers.826271/

I was generally of the mindset that any pot lubricant should be conductive but that's not really the case it seems as that would potentially bridge contacts to other contacts or areas that weren't intended. The pressure of the wiper on the trace essentially displaces the grease to leave such a minimal film thickness that it doesn't actually insulate the intended signal from between wiper contact and trace.

I used the Super Lube 21030 Multi-Purpose Synthetic Grease. Rather than disassembling the pot to get this grease on to the track/trace, I used a small thin dental tool (toothpick would work) to place the grease at the bottom slit opening of the pot and then a few shots of compressed air to push it in the rest of the way to the pot body. Operated the pot a few times and the wiper distributed it the rest of the way.